This invention relates to a two-stroke engine and more particularly to an improved induction system for such an engine.
In two-cycle, crankcase compression internal combustion engines the fuel/air charge is drawn into the crankcase and is compressed during the stroke of the piston for transfer to the combustion chamber through one or more transfer or scavenge passages that interconnect the crankcase with the portion of the cylinder bore above the piston at certain phases of its stroke. Such engines have the advantages of extreme simplicity and, for that reason, are popular in many applications. However, the long path through wich the fuel/air mixture must travel before it enters the combustion chamber presents certain problems. For example, when operating at low temperatures and under certain other operating conditions, there is a tendency for a portion of the fuel to condense from the fuel/air mixture in the crankcase. If this condensed fuel is transferred into the combustion chamber through the transfer or scavenge passages, the fuel/air mixture is irregular in strength and poor running can occur. These problems are particularly acute under acceleration, deceleration or when operating at low speeds. Various devices have been proposed for transferring the condensed fuel, sometimes referred to as "drains" from the crankcase into the combustion chamber so as to insure smoother running. Although these devices have this purpose, they are not always truly effective since the drains themselves are unevenly and irregularly distributed to the combustion chamber.
The problems aforenoted are also prevalent in connection with two-cycle engines that are employed as the power unit of an outboard motor. In such applications, the cylinders are normally disposed with their axes lying in a horizontal plane and thus the transfer passages extend generally horizontally. As a result, there is always the possibility that drains or fuel condensate may accumulate in the transfer passage and be irregularly inducted into the combustion chamber. Thus, the problems aforenoted may be more pronounced with two-cycle engines employed in connection with outboard motors or other applications in which the transfer passages extend in a horizontal direction.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is another object of this invention to provide an induction system for an internal combustion engine in which condensates are not allowed to accumulate in the transfer or scavenge passages.
It is a yet further object of this invention to provide an improved induction system for a two-cycle, horizontally disposed internal combustion engine.